ALL four July 7 suicide bombers were tracked by security services a year before they attacked London - but intelligence officers decided there was nothing suspicious about their behaviour.

FEARS were last night growing over the ability to stop terror attacks after the security blunders that let the London bombers slip through the net.

The four men who brought carnage to streets of the capital on July 7 were watched by intelligence officers a year before they killed 52 people on Tube trains and a bus.

But security chiefs called off the operation after it was decided the gang posed no threat. Last week the Mirror revealed how 30-year-old ringleader Mohammed Sidique Khan was filmed with a terror suspect last year and spotted chatting to an al-Qaeda fixer. No action was taken against him.

And last night a police source said the other three bombers - Shehzad Tanweer, 22, Jermaine Lindsay, 19, and Hasib Hussain, 18 - were also being tracked.

They were on a list of up to 100 people throughout the country feared to be Islamic fanatics.

A fifth man, thought to be an al-Qaeda operative, was being watched. He is on the run, believed to be in Pakistan, and could return to attack Britain again.

Field agents kept an eye the men's behaviour for several weeks but decided there was nothing out of the ordinary and pulled the plug.

The police source said the four "did not fit the preconceived terrorist profile".

A year later, the gang travelled to London from Yorkshire carrying their deadly cargo of explosives in rucksacks and blew themselves up in the morning rush-hour.

Angry MPs last night called for an overhaul of the surveillance system for suspected terrorists.

Shadow homeland security minister Patrick Mercer said: "These men appear not to have been as unknown to the security services as was first thought.

"If this is true, it suggests there are many more questions that need to be asked about our intelligence preparations prior to July 7. We will be demanding that these questions are answered." And Liberal Democrat home affairs spokesman Mark Oaten said the blunder shows the need for more cash to carry out surveillance operations properly.

The MP said: "This shows the importance of giving our intelligence services more resources and more people on the ground so they have the manpower they need to do their job.

"The Government should learn protecting this country from terrorists is not just about new laws, it is about money as well." The police source also said there were no suspicions about the men's behaviour in the immediate run-up to the attack.

Tanweer was filmed arguing with a cashier about being short-changed at a petrol station hours before he blew himself up.

He was also seen playing cricket with friends the night before the attacks on the capital.

The source added: "The Russell Square bomber (Hussain) is actually seen going into shops and bumping into people."

It is known a fifth man must have been involved with all four suicide bombers.

Police found an unused explosive rucksack in the men's car which was abandoned at Luton.